Feed device for a pilger rolling mill



May 19, 1970 K. E. TEPPGARD 3,512,386

FEED DEVICE FOR A PILGERIRVOLLING MILL Filed Sept. 28. 1967 ON NN J a Pm o 3K m? m& mm

mvEmR kn ut ErL and Teppgard 1 JJJggAMY Pm ATTORNEYS United States Patent U.S. Cl. 72189 3 Claims ABSTRACT OF THE DISCLOSURE A pilger rolling mill, of the type wherein the stand is stationary whilst the blank reciprocates, has an improved feed device characterized in that the axial feed motion is independent of the rotational motion of the blank. An axial feed means and an independent rotation means are driven in synchronism with the rolling cycles of the mill.

The present invention relates to a feed device for a pilger rolling mill. In a pilger mill the work piece has to be rotated and also fed towards the rolls simultaneously with the reciprocating movement between the work piece and the rolls. There are with regard to the reciprocating movement two main types of pilger mills. The work piece or blank can be stationary and the rolls reciprocating or the stand can be stationary and the blank reciprocating. In the latter case there are ditficulties in feeding the blank towards the rolls, because the devices for feeding and rotating the work piece have to take part in the reciprocating movement. Heretofore there have been suggested for this purpose hydraulic means for the feeding and rotating motions, but this had not provided suflicient accuracy. There have also been suggested mechanical means which, however, had the inconvenience that the feeding and rotating movement were coupled in dependence of each other which has made it impossible to regulate one of the said motions without also changing the other.

According to the invention there is provided a feed device in which the axial feed motion is independent of the rotating motion, which simplifies the mechanism and makes the feed and rotation motions more exact and makes it possible to regulate each motion separately.

Closer details of the invention appear from the following specification with the appended drawings in which:

FIG. 1, is a schematic perspective view of a device according to the invention, and

FIG. 2, shows a detail of the mechanism.

The mill stand 4 shown in FIG. 1 is stationary. The rolls 5 are driven from a toothed segment 3 which is coupled to a crankshaft 2, driven by a motor 1. This device makes the rolls rotate back and forth. The invention is, however, not limited to mills having rolls rotating back and forth but may be used also in such mills which have continuously rotating rolls. By a transmission shaft 19 the motor also drives a cam disc 15 which, by a link mechanism, imparts a reciprocating motion to a feed unit which is slidably mounted in a frame not illustrated. The link mechanism comprises a lever arm 14 which is journalled on a pivot 20 and has a roller 21 running on the cam wheel 15 and urged in contact therewith by a spring 22. The upper end of the lever arm 14 is coupled to the feed unit by a link 23.

The feed unit comprises a gear box 10 for the axial feed and another gear box 7 for rotating the work piece or blank and a feed screw 8 aligned with the path of the reciprocating work piece. In order to permit the reciprocating motion of both gear boxes 7 and 10 they are driven by spline shafts 17 and 18 respectively, which shafts are driven from the motor by a central stationary gear box 30.

The gear box 7 carries a chuck 7a which is adapted to hold the mandrel 40 on which the work piece 41 is mounted, the chuck being rotated by the gear box. The gear box 10 comprises a threaded sleeve 100, which matches the screw 8 and is rotated by the gear box thereby feeding the screw 8 towards the stand. The gear box 7 is attached to the screw 8 and moves along therewith, so that the distance between the gear boxes 7 and 10 increases as the rolling proceeds.

For imparting rotation to the spline shafts 17 and 18, there are two similar devices, one of which is shown in FIG. 2. The cam plate 50 is fastened eccentrically on the axis 51 which is driven from shaft 19 by gear 13. A lever arm 52 is journalled on a pivot 53 and urged with a roller 54 at its lower end towards the cam plate 50 by a spring 55. A link 56 connects the upper end of the lever arm 51 to an arm 57 of a ratchet transmission 58 of any usual and known type for transferring a rocking movement to an intermittent one-way motion of shaft 18. The arm 57 has a slit 59 in which the end of the link is fastened by means of a bolt 60 or similar, and the bolt 60 can be moved along the slit 59 for changing the amplitude of the reciprocating movement of the ratchet transmission. A similar mechanism, actuated by cam plate 50a, drives shaft 17.

The shaft 51 rotates at the same angular speed as does the shaft 19, the cycles of the feed and rotation of the work piece being synchronous with the cycles of the rolls.

During operation the motor 1 drives the rolls 5 back and forth by means of the toothed segment 3. The link system 15, 14, 23 imparts a reciprocating movement to the feed unit comprising the gear boxes 7 and 10 and the screw 8. The rolls have, in a generally known way, a rolling groove which comprises a part of the circumference, the rest of the circumference comprising a release portion which is not in contact with the work piece during rolling. The reciprocating axial movement of the work piece is obtained by means of the cam disc 15 and also by the cooperation of the work piece with the rolls. For feeding the work piece a short distance closer towards the rolls and turning it somewhat around its axis during each rolling cycle, the spline shafts 17 and 18 are intermittently moved at the moments when the rolls are not in contact with the work piece. This intermittent movement is obtained by the transmissions 50-60.

The reduction takes place during the stroke when the feed unit moves away from the rolls, that is to the left in FIG. 1. During the return stroke in the opposite direction the action of the rolls on the Work piece is purely finishing. At the end positions between these strokes the release portions of the rolls face the work piece, and hence there is no contact between the rolls and the work piece in these positions. The axial feed and the rotation are so timed that the axial feed takes place in the right end position, i.e., before the reduction stroke begins, whilst the rotation takes place at the left end position, i.e., before the finishing stroke begins.

The work piece is rotated in order that it be evenly worked around the periphery, and that such irregularities in the circular shape which may arise during a reduction stroke are eliminated during the subsequent finishing stroke. In order to have the work piece rolled evenly around the circumference it is desirable that the rotation angle somewhat deviates from an even fraction of 360, so that the work piece does not return to the same angular position after a full turn. Hence, the turnin angle should be somewhat greater or smaller than for instance 60 or From the foregoing appears that the gear with the sleeve 10a all of the time has an unchanged axial position in relation to the reciprocating link 23, while the screw 8 and the gear 7 successively are brought closer to the roils by the intermittent rotation of the sleeve 10a. When a work piece is completely rolled the parts 7 and 8 of the feed unit must be brought back to their starting position. This is done by means of a separate clutch mechanism 24 comprising a clutch 11 for coupling the spline shaft 18 to the gear box 30 with the ratchet 58 and a clutch 12 for coupling the shaft 18 to a separate motor 16. During rolling the clutch 11 is engaged while the clutch 12 is disengaged. After rolling the clutch mechanism 24 is used for disengaging the clutch 11 and instead engaging the clutch 12, and the motor 16 drives the shaft 18 in the reverse direction, turning the sleeve 10a so that the screw 8 with the gear box 7 is brought back to its starting position.

The device is useful for all pilger mills equipped with a stationary roll stand and is especially suitable for a high reduction mill where the requirements for narrow tolerances are especially high, e.g., as for rolling thin walled tubes of steel or other materials. Especially for rolling tubes of zirconium or Zirconium alloys it has been found suitable to reduce the Section in one step with as high reduction rate as possible on a cylindrical mandrel the diameter of which corresponds as closely as possible to the inner diameter of the tube, so that the diameter reduction becomes as small as possible, whilst at the same time the area reduction is as high as possible, e.g., 75% or even 80% or more. In this way there is obtained a circumferential orientation of the hydride precipitations which arise in zirconium tubes, at the same time that a thin wall thickness is obtained. The invention contributes to these resuits by making it possible to precisely regulate the feed and the rotation of the work will!!! Will lllllllll t rm piece independently of each other, so that the best possibie conditions can be provided for obtaining a high quality of the product.

What I claim is:

1. Feed device for a pilger mill having a stationary stand and a reciprocating work piece, said feed device comprising a reciprocating feed unit to which the work piece is attached,

said feed unit having screw means for the axial feed of the work piece and rotation means for rotating the work piece;

two spline shafts provided along the path of said feed unit, and means for driving said spline shafts intermittently in synchronism with the rolling cycles when the work piece is out of contact with the rolls of the mill,

one of said spline shafts being coupled to the screw means and the other spline shaft being coupled to the rotation means.

2. Feed device as defined in claim 1 which further comprises means for regulating the extent of the motion imparted from each of said spline shafts to said screw means and said rotation means, said regulating means for regulating being independent of each other.

3. Feed device as defined in claim 1, further characterized in that said screw means consists essentially of an axial screw and a threaded bushing cooperating with said screw. 7

References Cited UNITED STATES PATENTS 822,878 6/1906 Briede 72 189 2,680,391 6/1954 Kaiser 72l89 LOWELLA. LARSON, Primary Examiner iii 

